Process for preparing anisotropic rare earth magnet material

ABSTRACT

An anisotropic rare earth magnet material is provided by a sputtering technique. The material has structural and magnetic anisotropy. Its composition is represented essentially by the following formula: 
     
         (R.sub.1-a O.sub.a).sub.b M.sub.1-b 
    
     wherein R means at least one of rare earth metal elements of Y and the lanthanide series of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu or a combination of Hf and at least one of the foregoing rare earth metal elements, M denotes Co or a combination of Co and at least one of Fe, Cu, Zr, Ti, Al and B, a is not greater than 0.05 (a≦0.05), and b ranges from 0.1 to 0.5 (b=0.1-0.5).

This is a division of Ser. No. 063,334, filed June 17, 1987, now U.S.Pat. No. 4,836,867.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to an anisotropic rare earth magnet materialhaving structural and magnetic anisotropy and also to a process for theproduction of same.

2. Description of the Prior Art

There are numerous intermetallic compounds of the rare earth metal(R)-Cotype or the rare earth metal(R)-Fe type, including RM₁₃, R₂ M₁₇, RM₅, R₅M₁₉, R₂ M₇, RM₃, RM₂, R₂ M₃, R₂ M₁.7, R₄ M₃, R₂₄ M₁₁, R₉ M₄, R₃ M, etc.,wherein M is Co or Fe. Their crystalline structures are diverse andinclude the cubic, hexagonal, orthorhombic and rhombohedral systems.

Rare earth magnets are magnet materials which contain both hexagonal andrhombohedral crystals, make use of R₂ M₁₇, RM₅, R₂ M₇, RM₃ and the likeamong intermetallic compounds in many instances, and have largecrystalline and magnetic anisotropy. Compared with conventionalBa-ferrite magnets or Sr-ferrite magnets, Alnico-5, -6, -8 and -9magnets, two-phase separated magnets of Fe-Cr-Co, Pt-Co magnets andMn-Al-C magnets, their magnetic characteristics including those of boththe RM₅ and R₂ M₁₇ systems are significantly higher in coercive forceIHc and maximum energy product (BH)max. The consumption of rare earthmagnets has hence increased. Rare earth magnets have contributedconsiderably toward the size reduction of new industrial products andthe improvements of their characteristics.

As the usual production processes of RM₅ and R₂ M₁₇ which are producedcurrently, there may be mentioned primarily the sintering process andthe polymer bonding process which makes use of a binder. According tothe sintering process, raw materials are converted into roughly-groundpowder by melting the raw materials or reducing oxidized powderdirectly. In order to protect rare earth metals which are active andsusceptible to oxidation, the powder is finely ground into fine powder(5-20 μm) in an organic solvent such as silicone oil. After drying, thefine powder is press-formed along an axis of easy magnetization such asC-axis in a magnetic field of 10-30 kOe (800-2400 kA/m), followed bysintering, solid solution treatment and aging in a nonoxidizingatmosphere to obtain structural and magnetic anisotropy. In addition tothe above-described magnetic field pressing method, the unidirectionalsolidification method in which a magnet material is formed from a meltby the Bridgeman method, high-frequency zone melting method or the likemay also be mentioned as a method for orienting crystals in onedirection.

The polymer bonding process was developed to overcome the drawback ofbrittleness of sintered magnets. A prismatic portion which has grown inone direction from a melt is ground. The thus-formed powder is thenhardened thermally or chemically with a resin binder, a rubbery andthermoplastic binder, respectively.

A description will next be made of the mechanism of magnetization of asintered magnet. In the above-described rare earth magnets, themechanism of their coercive force generation may be discussed separatelyunder two different situations. One of the situations arises when thecoercive force is relatively low, i.e., about 6 kOe (480 kA/m). Underthis situation, a cellular micro-structure is formed with a rhombohedralcell of R₂ M₁₇ phase surrounded by boundaries of hexagonal crystals ofRM₅. When the coercive force is large, namely, higher than 14 kOe [>14kOe (>1120 kA/m)], the cell size increases and a thin lamellar layer ofRM₃ occurs in a manner superposed in the cell structure. Namely, thereversal of magnetization takes place when new domain walls come out incrystal grains and then grow. Domain walls in the stage of their growthcan move easily within their respective crystal grains. Theabove-mentioned cell boundaries however resist the movement of thedomain walls, thereby exhibiting strong pinning action against thedomain walls. The coercive force is determined by the size ( 500-2000 Å)of the cell. The coercive force is generally said to increase as thecell size becomes greater.

Magnetism as high as 30-35 MGOe (240-280 kJ/m³) in terms of maximumenergy product (BH)max is obtained at room temperature by such amechanism of magnetization as described above. However, rare earthmagnets are theoretically considered to have the capability to achieve(BH)max as large as 50-70 MGOe (400-560 kJ/m³). As a matter of fact, Dy₃Al₂ has been found to show a coercive force of 20 kOe (1600 kA/m),namely, (BH)max of 73 MGOe (584 kJ/m³) at a low temperature (thetemperature of liquefied helium). The mechanism of this magnetization isbelieved to be different from the conventional theory. Judging also fromthe fact that this phenomenon is very remarkable at low temperatures butthe magnetism is reduced due to thermal agitation when the temperatureis high, the pinning action against domain walls is not attributedsolely to cell boundaries as has been observed in the conventionalmechanism of magnetization but may also be attributed to stacking fault,Guinier-Preston (G.P.) zone and phase boundaries and also todislocation, etc. Owing to this pinning action, the magnetism to beproduced seems to reach a value close to the theoretical value and themechanism of its magnetization is believed to differ from the presenttheory of magnetism.

Although the above-described sintering process has such merits that itis excellent in mass productivity, features high yield and can easilymeet the requirement for various shapes, the sintering process tends tocause oxidation of powder being processed because the powder is fine, itis difficult to control oxygen in the grinding, drying and heattreatment steps. Since the powder is pressed and then sintered, it istechnically difficult to obtain thin products of 1 mm and less due toslipping upon pressing, cracking upon sintering and the brittlenessinherent to metal compounds. In addition, the powder oriented along theC-axis upon its sintering grows in random directions. The anisotropy istherefore prone to disturbance and the magnetism is deterioratedaccordingly.

On the other hand, the polymer bonding process is accompanied bydrawbacks that the magnets are thermally unstable (maximum servicetemperature: 200° C.) and compared with sintered magnets, have lowerdensities and lower magnetic characteristics.

SUMMARY OF THE INVENTION

In one aspect of this invention, there is thus provided an anisotropicrare earth magnet material having structural and magnetic anisotropy anda composition represented essentially by the following formula:

    (R.sub.1-a O.sub.a).sub.b M.sub.1-b

wherein R means at least one of rare earth metal elements of Y and thelanthanide series of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb and Lu or a combination of Hf and at least one of the foregoing rareearth metal elements, M denotes Co or a combination of Co and at leastone of Fe, Cu, Zr, Ti, Al and B, a is not greater than 0.05 (a≦0.05),and b ranges from 0.1 to 0.5 (b=0.1-0.5).

By artificially controlling the crystalline structure to contain oxides,the present invention has developed pinning action against domain wallsand created the domain structure.

In another aspect of this invention, there is also provided a processfor the production of an anisotropic rare earth magnet material, whichcomprises:

(i) providing in an Ar atmosphere a target having a compositionrepresented essentially by the following formula:

    (R.sub.1-a O.sub.a).sub.b M.sub.1-b

wherein R means at least one of rare earth metal elements of Y and thelanthanide series of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb and Lu or a combination of Hf and at least one of the foregoing rareearth metal elements, M denotes Co or a combination of Co and at leastone of Fe, Cu, Zr, Ti, Al and B, a is not greater than 0.05 (a≦0.05),and b ranges from 0.1 to 0.5 (b=0.1-0.5); and

(ii) applying an a.c. or d.c. electric field between the target and asubstrate in accordance with a sputtering technique, whereby a materialhaving structural and magnetic anisotropy is formed on the substrate.

According to the present invention, an electric field is applied betweena target and its associated substrate. Atoms, which have been thrown outof the target as a result of Ar⁻ bombardment, are allowed to deposit andgrow on the substrate. Here, crystallization is believed to take placeby heat so that the hexagonal structure grows. By the anisotropy incomposition owing to the growth of prismatic crystals and the existenceof the hexagonal structure grown in the direction of the C-axis, asputtered anisotropic magnet is therefore provided. The presentinvention has very important industrial significance in that ananisotropic magnet is produced directly from a vapor phase.

There are numerous industrial applications of this invention. Since themagnet material of this invention can provide smaller magnets, it isuseful as magnets for micromotors, bias magnets like magnetoresistors, amagnetostrictive material, etc. The magnet material of this inventioncan be secured directly to substrates. Various processing and machiningsteps can hence be omitted, leading to simplification of the processingand machining and also to a reduction to the manufacturing cost. As anextension of the sputtering technique, the process of the presentinvention is effective for the production of materials which cannot bemachined into thin sheets, especially, thick films (300-500 μm).

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 schematically illustrates a radio frequency (hereinafterabbreviated as "rf") sputtering apparatus suitable for use in thepractice of this invention;

FIG. 2 diagrammatically illustrates measurement results of the thicknessdistribution of sputtered films;

FIG. 3 is a graph showing the sputtering output and time dependency ofthe thickness of a sputtered film;

FIG. 4 diagrammatically shows the relation between the composition,thicknesses and IHc of a sputtered (SmO)Co film;

FIG. 5 is a line analysis electron micrograph of the metal structure ofthe sputtered (SmO)Co film;

FIG. 6 is a graph depicting results of line analyses of Sm and O in the(SmO)Co sputtered film;

FIG. 7 is an electron micrograph showing results of a plane analysis ofSm in the metal structure of the (SmO)Co sputtered film;

FIG. 8 is an electron micrograph showing results of a plane analysis ofoxygen in the metal structure of the (SmO)Co sputtered film;

FIG. 9 shows diagrammatically temperature variations on a substrate;

FIG. 10 is a graph showing the temperature of the substrate as afunction of the sputtering output;

FIG. 11 is a graph showing the temperature change of the substratedepending on positions on the substrate;

FIG. 12 diagrammatically illustrates differences in crystallinestructure depending on positions on the substrate;

FIG. 13 is a graph showing results of X-ray diffraction analyses ofsputtered films formed at varied sputtering outputs respectively;

FIGS. 14-a to 14-b are electron micrographs showing the metal structuresof sputtered films formed at different sputtering outputs;

FIG. 15 is a B-H curve of a sputtered Sm-Co film; and

FIG. 16 is a graph showing magnetic characteristics (horizontaldirection) as a function of the sputtering output.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As methods for artificially controlling the crystalline structure, theremay be mentioned the liquid quenching method in which a melt is blownagainst a roll, sputtering, and ion plating methods, such as vacuumevaporation, chemical vapor deposition (CVD), molecular beam epitaxy,arc plasma plating, cluster ion beam plating, etc. In view of theeasiness and reproducibility upon controlling the thickness andtemperature of a material to be formed and its transformation ofamorphous phase→non-equilibrium phase→crystalline phase, rf sputtteringhas been found most suitable. Needless to say, other methods are alsoapplicable.

It is also possible to use the opposed targets technique in whichtargets are disposed opposite to each other. Owing to the opposingarrangement of the targets, the generation of plasma is increasedcompared with the use of a single target. As a result, more plasma isallowed to flow toward substrates arranged around the targets and thedeposition rate becomes higher than that available by usualrf-sputtering techniques. The opposed targets technique is thereforepreferred.

A description will next be made of a process for the production oftargets useful in the practice of this invention.

The composition of the anisotropic rare earth magnet material of thisinvention is (RO)M. Therefore, R and O are in an nonseparable relation.Needless to say, inclusion of O is said to give influence to theformation of prismatic crystals. An R_(1-a) O_(b) compound is said to beeffective in the pinning of domain walls and is hence effective for theimprovement of coercive force. It is therefore essential for thecompound to contain O in an amount of 5% or less. O is however veryreactive with rare earth metals and the crystalline structure, magneticcharacteristics and the like are affected by variations in the Ocontent. In order to achieve a desired O content, the proportion of O isadjusted upon preparation of targets.

For the preparation of targets, a rare earth metal R of 99.9% purity andseveral kinds of metals M of 99.99% purity are weighed first of all.They are subjected to induction melting in an Ar atmosphere. Afterstirring the resultant melt into a homogeneous melt, the homogeneousmelt is cast in a mold. The thus-obtained ingot is coarsely ground topass through a 48 mesh screen or so and is then finely ground to 5-20 μmparticles in an organic solvent by means of an attritor, ball mill orthe like. After drying, the resultant powder is press-formed and thensintered so that the content of oxygen can be controlled at a desiredlevel. The sintered targets are bonded respectively to target holders,whereby the preparation and setting of the targets are completed.

Substrates will next be described. As substrates, there are metal (Cu,Al) substrates, fine polymer substrates, fine ceramics substrates,ceramic porcelain substrates, quartz glass substrates, "Pyrex" (trademark) substrates, sheet glass (usual soda glass) substrates, Sisubstrates, carbon substrates, etc. These substrates can all be usedsatisfactorily. Glass substrates such as sheet glass were provided assamples, because such glass substrates are most suitable in view oftheir lower prices and good processability and their high applicabilityfor measurement of various physical properties.

Using the target and substrate as described above, rf sputtering isconducted. The outline construction of a sputtering apparatus usable inthe practice of this invention is schematically shown in FIG. 1. Thissputtering apparatus is used to conduct the usual sputtering method inwhich a target 1 and a substrate 2 are arranged opposite to each other.Sputtering is effected in the following sequence. First, the sputteringapparatus is roughly evacuated through an exhaust pipe 3 by means of arotary pump (not shown). Vacuum evacuation is then conducted to about2×10⁻⁶ torr by an unillustrated diffusion pump. Ar gas is fed through apipe 4 so as to purge the interior gas with Ar gas, so that the interiorpressure is maintained at 1-5×10⁻² torr. After etching and cleaning thesubstrate 2 and target 1, sputtering is started so that (RO)M begins todeposit on the substrate 2. The deposition rate varies depending on theenergy of the radio frequency. The quantity of a deposit increaseslinearly as the time goes on. In FIG. 1, designated at numerals 5, 6 arefeed tubes for cooling water while numeral 7 indicates a high-frequencypower source.

FIG. 2 illustrates, by way of example, the thickness distribution of afilm sputtered by using a target the diameter of which was 120 mm. Aparabolic distribution curve is shown. A dial gauge with graduations inμm was used for the measurement of the film thickness.

FIG. 3 depicts the relation between film thickness and rf-sputteringoutput and time. Each output was read from a meter of an rf powersource. Plotted dots correspond to points right underneath the target,where maximum values were obtained respectively. The film thickness issubstantially in a linear relation with both sputtering time andsputtering output.

The composition of each sputtered film was then studied by usual X-rayfluorescence analysis and chemical analysis in combination. The X-rayfluorescence analysis was carried out by preparing a calibration curvewith a standard sample. The chemical analysis was conducted by a wetmethod. Oxygen was measured using a gas analyzer Coulomatic "O" (tradename). Each sample was removed from its corresponding glass substrateand was then subjected to the measurements.

Results of the X-ray fluorescence analysis of a ternary system (SmO)Rare shown by way of example in FIG. 4. Shown below the results of thecomposition analysis is a graph illustrating the relation between thefilm thickness and the IHc determined from the measurement of the B-Hmagnetic characteristic. The composition of the target employed was Sm:36.5%, O: 1.0% and Co: balance. As the film thickness decreased, theproportions of Sm and O tended to increase while the proportion of Coinclined to decrease. X-ray fluorescence analysis cannot provide anycorrect analysis data when the film thickness increases to about 20 μm.X-ray fluorescence analysis was therefore unable to determine the exactrelation between film thickness and composition. The oxygen contentincreased about 1.5 times compared with the oxygen content of thetarget. This can also be attributed to leakage of the sputteringapparatus and segregation of oxygen in the sintered target. As a resultof an EPMA analysis, it was confirmed that oxygen is dispersed almostuniformly in the sputtered film.

FIG. 5 is a line analysis scanning electron micrograph of the sputtered(SmO)Co film, FIG. 6 shows results of line analyses, FIG. 7 depictsresults of a plane analysis of Sm, and FIG. 8 illustrates results of aplane analysis of oxygen. From the results of the line analysis, Sm andoxygen are both substantially uniformly dispersed. Also, based on theresults of the plane analyses, their dispersion is also considered to beuniform substantially from the boundary with the glass substrate to theentire area of the sputtered film.

The crystalline structure of the thus-sputtered film will next bedescribed. As also shown in FIG. 2, it has been found that the thicknessdistribution of a film varies depending on the position on an associatedsubstrate, the sputtering temperature changes in accordance with thesputtering output and time, and the crystalline structure is affectedaccordingly.

FIG. 9 shows measurement results of temperature variations on a glasssubstrate, which occurred by the initiation and stop of sputtering.Sudden temperature jump and drop are both observed. By providing athermocouple on a substrate right underneath a target, output-dependenttemperature variations were then measured. Results are shown in FIG. 10.The temperature of the substrate increased almost linearly in proportionto the sputtering output and reached about 600° C. at 1.0 kW-hour. Thetemperature distribution on the substrate was also investigated. Thetemperature changed considerably depending on positions with respect tothe target as shown in FIG. 11. Outside the outer periphery of thetarget, the temperature dropped. As a result, the crystalline structureof the sputtered film changed. The crystalline structures at Point A(corresponding to a target center) and Point B (10 mm apart from theouter periphery of the target) in FIG. 11 are respectively shown in FIG.12. At Point A, the sputtered film had a crystalline structure with 2-17phase. At Point B, a diffraction pattern characteristic to an amorphousstructure was shown. Namely, the difference between the crystallinestructures at Points A and B in FIG. 12 is believed to be affectedconsiderably by the temperature of the substrate in view of thevariations in composition shown in FIG. 4 and the measurement results oftemperature distribution in FIG. 11. Namely, crystallization takes placeto undergo crystal growth into an intermetallic compound such as 2-17phase when the temperature of the substrate is high upon sputtering.Outside the outer periphery of the target, the temperature of thesubstrate is too low to crystallize a sputtered film, so that thesputtered film takes an amorphous structure. This also arises when thetemperature of a substrate is changed by varying the sputtering output.FIG. 13 shows results of X-ray analyses which were conducted by changingthe sputtering output in five stages from 0-1.0 kW. As the sputteringoutput increased, more peaks appeared in the diffraction pattern of theamorphous structure and their intensities became stronger. The planescorresponding to the thus-produced peaks can be identified as hexagonalcrystals by indexes in accordance with the Hull-Davey's chart. When thetargets used were 2-7 phase (40% Sm) and 1-5 phase (36% Sm), it seemedthat their crystalline structures in the high temperature range remainedto have the hexagonal system instead of the rhombohedral system evenafter the temperature was lowered to room temperature.

The structures and magnetic characteristics of sputtered films will nextbe described. FIGS. 14-a, 14-b and 14-c show scanning electronmicrographs of broken-out sections of films prepared by conductingsputtering at outputs of 0.2, 0.6 and 1.0 kW, respectively, for 10hours. Under each of these output conditions, a prismatic crystallinestructure of about 0.5 μm wide is observed. Accordingly, littledifferences in width appear to arise depending on the sputtering output.It has been confirmed from the above observation that the structure ofeach sputtered film contained prismatic crystals in the directionperpendicular to its corresponding substrate and was hence anisotropicstructurally.

FIG. 15 shows a B-H curve measured by a vibrating sample magnetometer(VSM). The sample measured was obtained from a portion of a sputteredfilm, which portion lied right underneath the associated target. It wasthen cut into a desired shape. The film thickness was then measured by adial gauge and its volume and weight were calculated roughly from thedensities of the glass substrate and sputtered film. Included in thecharacteristics measured were 4πIs, 4πIr, (BH)max, BHc, IHc and HK (H at4πIr x 0.9: squareness), all at Hm=18 kOe (1440 kA/m). Thesecharacteristics were measured in directions parallel and perpendicularto the substrate.

FIG. 16 illustrates magnetic characteristics when the sputtering outputwas changed. 4πIs at Hm=18 kOe (1400 kA/m) remained substantiallyconstant irrespective of the sputtering output, but 4πIr, (BH)max, IHc,BHc and HK were improved at the sputtering outputs of 0.6 kW and higher.Similar to the results of the X-ray diffraction, it seems to be possibleto conclude that magnetic characteristics as a magnet material weredeveloped as the crystallization went on.

The present invention will hereinafter be described in further detail bythe following Examples.

EXAMPLE 1

An alloy, the composition of which was 35 wt. % Sm and the balance Co,was subjected to induction melting in an Ar atmosphere. The resultantingot was coarsely ground by a stamp mill and then finely ground insilicone oil into powder having an average particle size of 10-15 μm.After drying, the fine powder was press-formed in a mold having an outerdiameter of 140 mm. The green compact was sintered at 1100° C. for 1hour in vacuum or in an atmosphere of an inert gas and was then allowedto cool down in the same furnace. The composition of the thus-obtainedsintered body was 35 wt. % Sm, 0.9 wt. % O and the balance Co. Itsdiameter was 120 mm. Both upper and lower sides of the sintered bodywere polished to provide a target.

Sputtering was conducted in a vacuum of 2×10⁻² torr in an Ar atmosphere.The sputtering was continued for 50 hours at a sputtering output of 0.8kW. As a result, a sputtered film was deposited to a thickness of 350μm. Its magnetic characteristics were measured by a VSM in a directionparallel to the sputtered surface. The following results were obtained.

Br: 8500 Gausses (0.85 Tesla)

(BH)max: 9.9 MGOe (79.2 kJ/m³)

BHc: 3000 Oe (240 kA/m)

IHc: 4400 Oe (352 kJ/m³)

HK: 1400 Oe (112 kA/m)

EXAMPLE 2

An alloy, the composition of which was 40 wt. % Sm and the balance Co,was processed in the same manner as in Example 1, thereby obtaining asintered body. The composition of the thus-obtained sintered body was 40wt. % Sm, 1.1 wt. % O and the balance Co and its diameter was 120 mm.

A target was fabricated with the above-obtained sintered body.Sputtering was then conducted at 0.8 kW for 5 hours. The film thicknessreached 38 μm and the following results were obtained.

Br: 6500 Gausses (0.65 Tesla)

(BH)max: 6.0 MGOe (48 kJ/m³)

BHc: 4000 Oe (320 kA/m)

IHc: 10700 Oe (856 kA/m)

EXAMPLES 3-9

In the same manner as in Examples 1 and 2, the following samples wereprepared and their magnetic characteristics were measured. The followingdata were obtained.

    ______________________________________                                        Example    Resultant composition                                                                        Film thickness                                      No.        (wt. %)        (μm)                                             ______________________________________                                        3          Nd.sub.35 Fe.sub.15 Co.sub.bal B.sub.2 O.sub.0.7                                             150                                                 4          Pr.sub.33 Fe.sub.14 Co.sub.bal B.sub.4 O.sub.0.6                                             170                                                 5          Gd.sub.36 Fe.sub.15 Co.sub.bal B.sub.3 O.sub.0.8                                             350                                                 6          Tb.sub.34 Fe.sub.12 Co.sub.bal B.sub.1 O.sub.2.1                                             500                                                 7          La.sub.34 Fe.sub.16 Co.sub.bal B.sub.5 O.sub.1.5                                             100                                                 8          Ce.sub.35 Fe.sub.15 Co.sub.bal B.sub.2 O.sub.0.9                                             300                                                 ______________________________________                                    

    ______________________________________                                        Ex-   Magnetic Characteristics                                                ample Br         (BH)max     BHc     IHc                                      No.   Gauss (Tesla)                                                                            MGOe kJ/m.sup.3)                                                                          Oe (kA/m)                                                                             Oe (kA/m)                                ______________________________________                                        3     16000 (1.6)                                                                              30 (240)    2000 (160)                                                                            3000 (240)                               4     11000 (1.1)                                                                              24 (192)    3000 (240)                                                                            6000 (480)                               5     6000 (0.6) 10 (80)     2000 (160)                                                                            4000 (320)                               6     5000 (0.5) 12 (96)     3500 (280)                                                                            5000 (400)                               7     7000 (0.7)  7 (56)     1300 (104)                                                                            2300 (184)                               8     6000 (0.6)  5 (40)     1000 (80)                                                                             3000 (240)                               ______________________________________                                    

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the inventionas set forth herein.

What is claimed is:
 1. A process for the production of an anisotropicrare earth magnet material, which comprises:(i) providing in an Aratmosphere a target consisting essentially of a composition having thefollowing formula:

    (R.sub.1-a O.sub.a).sub.b M.sub.1-

wherein R is (1) at least one rare earth metal element selected from thegroup consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,Tm, Yb and Lu, or (2) a combination of Hf and at least one of said rareearth metal elements, M is (1) Co, or (2) a combination of Co and atleast one of Fe, Cu, Zr, Ti, Al and B, a is from 0.02 to 0.05, and b isfrom 0.1 to 0.5; and (ii) while maintaining said target and saidsubstrate in said Ar atmosphere, applying an a.c. or d.c. electric fieldbetween said target and a substrate in accordance with a sputteringtechnique, under conditions effective to form on said substrate amaterial of said composition, said material being a magnetic filmexhibiting structural and magnetic anisotropy and comprising a hexagonalcrystalline phase.
 2. A process as claimed in claim 1 in which saidmaterial is anisotropic both structurally and magnetically, and saidmaterial has a prismatic crystalline structure.
 3. A process as claimedin claim 1 in which said material is anisotropic both structurally andmagnetically, and said material has a multiphase structure of amorphousstructural phase and hexagonal structural phase.
 4. A process as claimedin claim 1 wherein a is from 0.0217 to 0.0423, and b is from 0.355 to0.411.
 5. A process as claimed in claim 1 in which said composition isselected from the group consisting of

    Sm.sub.35 O.sub.0.9 CO.sub.balance, and

    Sm.sub.40 O.sub.1.1 Co.sub.balance.


6. A process as claimed in claim 1 in which said composition is

    Gd.sub.36 Fe.sub.15 Co.sub.bal B.sub.3 O.sub.0.8.


7. A process as claimed in claim 1 in which said composition is

    La.sub.34 Fe.sub.16 Co.sub.bal B.sub.5 O.sub.1.5.


8. A process as claimed in claim 1 in which said composition is

    Ce.sub.35 Fe.sub.15 Co.sub.bal B.sub.2 O.sub.0.9.


9. A process as claimed in claim 1 in which the sputtering technique isrf sputtering under an Ar gas pressure of from 1 to 5×10⁻² torr.
 10. Aprocess as claimed in claim 1 in which said target is prepared bysintering particles of an alloy consisting of the R and M metals, underconditions effective to form said composition.
 11. A process as claimedin claim 1 in which said target contains from 33 to 40 percent by weightof R.